This invention is concerned with improvements in or relating to gas flow detectors adapted to detect an excessive flow of gas. The invention may particularly find application in steam flow detectors for use in steam flow lines adjacent steam traps, to detect an unacceptable level of leakage of steam through the traps. However, similar flow detectors might find application in, for example, compressed air lines where similar problems can arise. By the term "gas" where used herein is merely meant a fluid in a gaseous state, and the term is to be understood specifically to include both steam and air.
To avoid wastage of steam, it is desirable to check steam traps at intervals for leaks. Efficient operation of a steam trap can be checked, without disassembling the trap, by various methods (for example, ultrasonic methods) but these require special equipment and a skilled operator.
For detecting steam trap leakage, detectors are available which can be permanently installed adjacent a trap in a steam flow line. However, with known detectors problems can arise from the fact that where the detector is to be added to an existing flow line, there is frequently found to be only a very short length of horizontal pipe available for removal and replacement by a detector. Sometimes installation is further complicated by another piece of equipment, for example a filter, close to the steam trap in the flow line. Accordingly it is very desirable that a detector be of short length, so that usually it can be readily inserted without substantial modification of the existing arrangement of pipework and equipment.
Available detectors tend to be of such length that one is commonly unable to insert them into an existing flow line without substantially modifying the existing arrangement of pipework and equipment. Such modification work necessarily increases the difficulty of installing the detector, and puts up the cost of the installation operation. Furthermore, available detectors tend to be of a relatively expensive construction.
For example, one known kind of detector for use in association with a steam trap is described in British patent application No. 2 022 846. That detector is arranged to operate on a U-tube principle. Any steam passing through the detector in normal use passes through an aperture in a baffle which extends into a well containing condensate. An electrode is positioned within the well on the inlet side of the baffle to signal, in normal use of the detector with little or no steam passing through, that it is covered by condensate. Should the steam flow through an associated trap become excessive, the pressure drop at the outlet of the detector will cause the condensate level on the outlet side of the baffle to rise, and the level on the inlet side of the baffle to fall correspondingly. The fall in level on the inlet side causes the electrode to become uncovered and a signal is given.